1. Field of the Invention
This invention relates to the field of irrigation control devices. More particularly, it relates to a device that controls power applied to an electrically operated control valve as a function of soil moisture with the moisture sensing and detecting being physically remote from the level setting and valve control. It inhibits valve power when there is adequate moisture in the soil for which it controls irrigation and allows the power to be applied as long as irrigation is needed.
2. Description of the Prior Art
Field of Search
137/78.1, 78.3; 239/63: 324/690
Search References
U.S. Patent Documents
U.S. Pat. No. 4,838,296 Jun. 13, 1989 Brooks PA1 U.S. Pat. No. 4,852,802 Aug. 1, 1989 Iggulden et al PA1 U.S. Pat. No. 5,060,859 Oct. 29, 1991 Bancroft PA1 U.S. Pat. No. 4,952,868 Aug. 28, 1990 Scherer, III PA1 U.S. Pat. No. 4,684,920 Aug. 4, 1987 Reiter
The prior art discloses circuits for controlling irrigation devices.
U.S. Pat. No. 4,838,296 discloses a system for controlling an electrically operated irrigation valve in response to input power from a clocking device and soil moisture conditions. It also discloses a varying resistance sensing element. Note, however, that the control uses AC power from a clocking device and that power is applied to the valve, control, and sensing device without isolation. Once it has applied power to a valve it will continue until input power is removed by the clocking device. The sensing and level detecting circuit is not remote from the level setting and valve control circuit. The sensing element uses a ceramic block and is powered by AC.
U.S. Pat. No. 4,852,802 discloses a system for controlling an electrically operated irrigation control valve in response to soil moisture conditions. Note however that the control and sensor circuits and the sensing element are not disclosed. The disclosed sensor and combined sensor and control receives its power from batteries. The combined sensor and control can not control a standard AC powered irrigation valve. The separate sensor and control communicate via radio frequency and the sensor moisture level can not be adjusted remotely.
U.S. Pat. No. 5,060,859 discloses a system for controlling an electrically operated irrigation valve in response to input power from a clocking device and soil moisture conditions. It also discloses varying resistance sensing elements. Note, however, that it does not disclose the sensing element. The control uses AC power from a clocking device and that power is applied to the valve, control, and sensing device without isolation. Once power is applied to a valve it is latched on and will continue until input power is removed by the clocking device. The sensing and level detecting circuit is not remote from the level setting and valve control circuit.
U.S. Pat. No. 4,952,868 discloses a varying resistance sensing element to be used in conjunction with an electrically operated irrigation valve control Note however that it does not control an irrigation valve as a function of moisture.
U.S. Pat. No. 4,684,920 discloses a remotely controlled bypass for a system for controlling an electrically operated irrigation valve in response to input power from a clocking device and soil moisture conditions. Note however that it does not control an irrigation valve as a function of moisture.